1. Field of the Invention
The invention relates in general to an image processing method, and more particularly to an image processing method for reducing jaggy effect.
2. Description of the Related Art
Processing of image edges plays a very important role when it comes to achieving a high quality image. Particularly, the processing quality of high-contrast image edges of pictures or texts is crucial to image quality. In order to reduce computing time, ordinary ink-jet printers normally halftone process a document-to-be-printed to obtain a halftone binary image, and then have the document-to-be-printed printed out under a low-resolution printing mode. However, jaggy effect always occurs at the edges of the halftone binary image, which is not desired in a high quality image.
To resolve the jaggy effect, a method of encoding high-resolution edge position information in continuous tone image information is provided in U.S. Pat. No. 6,020,979. FIG. 1 shows a plurality of edge patterns, which could possibly be used in U.S. Pat. No. 6,020,979. Nevertheless, this method, which can regulate the edge position along fast scanning direction X only but cannot regulate the edge position along slow scanning direction Y, still cannot completely resolve the above-mentioned jaggy effect problem.
In addition, a method and apparatus for the resolution enhancement of gray-scale images that include text and line art is provided in U.S. Pat. No. 5,742,703, while liquid ink printing system having region-dependent image processing is provided in U.S. Pat. No. 5,778,160. However, the technologies disclosed in both patents involve segmentation operation and template matching procedure, which are complicated in nature, require a large amount of computing time and are energy-consuming as well. How to design a simple yet efficient method to resolve the jaggy effect in the output image of ink-jet printer has thus become an imminent challenge to professionals in the industry.